package org.apache.lucene.search.spans;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;

import java.util.Collection;
import java.util.Set;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.Query;
import org.apache.lucene.util.ToStringUtils;

/** Removes matches which overlap with another SpanQuery. */
public class SpanNotQuery extends SpanQuery {
	private SpanQuery include;
	private SpanQuery exclude;

	/**
	 * Construct a SpanNotQuery matching spans from <code>include</code> which
	 * have no overlap with spans from <code>exclude</code>.
	 */
	public SpanNotQuery(SpanQuery include, SpanQuery exclude) {
		this.include = include;
		this.exclude = exclude;

		if (!include.getField().equals(exclude.getField()))
			throw new IllegalArgumentException("Clauses must have same field.");
	}

	/** Return the SpanQuery whose matches are filtered. */
	public SpanQuery getInclude() {
		return include;
	}

	/** Return the SpanQuery whose matches must not overlap those returned. */
	public SpanQuery getExclude() {
		return exclude;
	}

	public String getField() {
		return include.getField();
	}

	/**
	 * Returns a collection of all terms matched by this query.
	 * 
	 * @deprecated use extractTerms instead
	 * @see #extractTerms(Set)
	 */
	public Collection getTerms() {
		return include.getTerms();
	}

	public void extractTerms(Set terms) {
		include.extractTerms(terms);
	}

	public String toString(String field) {
		StringBuffer buffer = new StringBuffer();
		buffer.append("spanNot(");
		buffer.append(include.toString(field));
		buffer.append(", ");
		buffer.append(exclude.toString(field));
		buffer.append(")");
		buffer.append(ToStringUtils.boost(getBoost()));
		return buffer.toString();
	}

	public Spans getSpans(final IndexReader reader) throws IOException {
		return new Spans() {
			private Spans includeSpans = include.getSpans(reader);
			private boolean moreInclude = true;

			private Spans excludeSpans = exclude.getSpans(reader);
			private boolean moreExclude = excludeSpans.next();

			public boolean next() throws IOException {
				if (moreInclude) // move to next include
					moreInclude = includeSpans.next();

				while (moreInclude && moreExclude) {

					if (includeSpans.doc() > excludeSpans.doc()) // skip
																	// exclude
						moreExclude = excludeSpans.skipTo(includeSpans.doc());

					while (moreExclude // while exclude is before
							&& includeSpans.doc() == excludeSpans.doc()
							&& excludeSpans.end() <= includeSpans.start()) {
						moreExclude = excludeSpans.next(); // increment exclude
					}

					if (!moreExclude // if no intersection
							|| includeSpans.doc() != excludeSpans.doc()
							|| includeSpans.end() <= excludeSpans.start())
						break; // we found a match

					moreInclude = includeSpans.next(); // intersected: keep
														// scanning
				}
				return moreInclude;
			}

			public boolean skipTo(int target) throws IOException {
				if (moreInclude) // skip include
					moreInclude = includeSpans.skipTo(target);

				if (!moreInclude)
					return false;

				if (moreExclude // skip exclude
						&& includeSpans.doc() > excludeSpans.doc())
					moreExclude = excludeSpans.skipTo(includeSpans.doc());

				while (moreExclude // while exclude is before
						&& includeSpans.doc() == excludeSpans.doc()
						&& excludeSpans.end() <= includeSpans.start()) {
					moreExclude = excludeSpans.next(); // increment exclude
				}

				if (!moreExclude // if no intersection
						|| includeSpans.doc() != excludeSpans.doc()
						|| includeSpans.end() <= excludeSpans.start())
					return true; // we found a match

				return next(); // scan to next match
			}

			public int doc() {
				return includeSpans.doc();
			}

			public int start() {
				return includeSpans.start();
			}

			public int end() {
				return includeSpans.end();
			}

			public String toString() {
				return "spans(" + SpanNotQuery.this.toString() + ")";
			}

		};
	}

	public Query rewrite(IndexReader reader) throws IOException {
		SpanNotQuery clone = null;

		SpanQuery rewrittenInclude = (SpanQuery) include.rewrite(reader);
		if (rewrittenInclude != include) {
			clone = (SpanNotQuery) this.clone();
			clone.include = rewrittenInclude;
		}
		SpanQuery rewrittenExclude = (SpanQuery) exclude.rewrite(reader);
		if (rewrittenExclude != exclude) {
			if (clone == null)
				clone = (SpanNotQuery) this.clone();
			clone.exclude = rewrittenExclude;
		}

		if (clone != null) {
			return clone; // some clauses rewrote
		} else {
			return this; // no clauses rewrote
		}
	}

	/** Returns true iff <code>o</code> is equal to this. */
	public boolean equals(Object o) {
		if (this == o)
			return true;
		if (!(o instanceof SpanNotQuery))
			return false;

		SpanNotQuery other = (SpanNotQuery) o;
		return this.include.equals(other.include)
				&& this.exclude.equals(other.exclude)
				&& this.getBoost() == other.getBoost();
	}

	public int hashCode() {
		int h = include.hashCode();
		h = (h << 1) | (h >>> 31); // rotate left
		h ^= exclude.hashCode();
		h = (h << 1) | (h >>> 31); // rotate left
		h ^= Float.floatToRawIntBits(getBoost());
		return h;
	}

}
